Pulmonary hypertension and the smooth muscle of the pulmonary arterioles in chickens at high altitude

1. 1. One-day-old male (m) and female (f) chickens from a population living at 3300m for several generations were raised at 3300 m (HA) and at sea level (SL). 2. 2. The histology of the pulmonary arterioles was studied in the HA and SL chickens when they were 4 weeks old and the thickness of their muscular coat (MT) determined. 3. 3. Pulmonary arterial pressure (Ppa), hematocrit (Hct) and the wet and dry weights of the total ventricle, left ventricle, septum and right ventricle (RV) were obtained when the HA and SL birds were 8 weeks old. 4. 4. Results indicated that chickens have a thick muscular coat in their pulmonary arterioles. MT expressed as a fraction of arteriolar diameter (MT/AD) was 0.113 at SL. Exposure to HA increased this value in the m (0.137, P < 0.01) but not in the f (0.123, P > 0.05). 5. 5. Ppa, RV and Hct were significantly higher at HA in both sexes. The degree of pulmonary hypertension and right ventricular hypertrophy observed was smaller than that found in earlier generations of these chickens studied several years ago. This probably indicates some degree of adaptation after generations of life at HA. © 1982.